Diabetic foot ulcers (DFUs) are among the most frequent complications of diabetes with significant morbidity and mortality. Diabetes can trigger neutrophils to undergo histone citrullination by protein arginine deiminase 4 (encoded by Padi4 in mice) and release neutrophil extracellular traps (NETs). The specific mechanism of NETs-mediated wound healing impairment in diabetes remains unknown. In this study, we show neutrophils are more susceptible to NETosis in diabetic wound environments. Via in vitro experiments and in vivo models of wound healing using wide-type and Padi4^-/- mice, we demonstrate NETs can induce the activation of PAK2 via the membrane receptor TLR-9. Then PAK2 phosphorylates the intracellular protein Merlin/NF2 to inhibit the Hippo-YAP pathway. YAP binds to transcription factor SMAD2 and translocates from the cytoplasm into the nucleus to promote endothelial-to-mesenchymal transition (EndMT), which ultimately impedes angiogenesis and delays wound healing. Suppression of the Merlin/YAP/SMAD2 pathway can attenuate NET-induced EndMT. Inhibition of NETosis accelerates wound healing by reducing EndMT and promoting angiogenesis. Cumulatively, these data suggest NETosis delays diabetic wound healing by inducing EndMT via the Hippo-YAP pathway. Increased understanding of the molecular mechanism that regulates NETosis and EndMT will be of considerable value for providing cellular targets amenable to therapeutic intervention for DFUs.

Neutrophil extracellular traps (NETs) play an important role in abdominal aortic aneurysm (AAA) formation; however, the underlying molecular mechanisms remain unclear. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) may exert therapeutic effects on AAA through their immunomodulatory and regenerative abilities. This study aimed to examine the role and mechanism of MSC-EVs in regulating the development of NET-mediated AAA. Excessive release of NETs was observed in patients with AAA, and the levels of NET components were associated with the clinical outcomes of the patients. Datasets from the Gene Expression Omnibus database were analyzed and revealed that the PI3K/AKT pathway and ferroptosis were strongly associated with NETosis during AAA formation. Further experiments verified that NETs promoted AAA formation by inducing ferroptosis in smooth muscle cells (SMCs) by inhibiting the PI3K/AKT pathway. The PI3K agonist 740 Y-P, the ferroptosis inhibitor ferrostatin-1, and Padi4 deficiency significantly prevented AAA formation. MSC-EVs attenuated AAA formation by reducing NET release in an angiotensin II-induced AAA mouse model. In vitro experiments revealed that MSC-EVs reduced the release of NETs by shifting NETosis to apoptosis. Our study indicates an important role for NET-induced SMC ferroptosis in AAA formation and provides several potential targets for AAA treatment.

We here examined the potential biological function of phosphoenolpyruvate carboxykinase 1 (PCK1) in angiogenesis. shRNA- or CRISPR-Cas9–induced PCK1 depletion potently inhibited endothelial cell proliferation, migration, sprouting, and tube formation, whereas ectopic PCK1 overexpression exerted opposite activity. In HUVECs, Gα _i3 expression and Akt activation were decreased following PCK1 depletion, but were augmented by ectopic PCK1 overexpression. In vivo, retinal expression of PCK1 gradually increased from postnatal day 1 (P1) to P5. The intravitreous injection of endothelial-specific PCK1 shRNA adenovirus at P1 potently inhibited the radial extension of vascular plexus at P5. Conditional endothelial knockdown of PCK1 in adult mouse retina increased vascular leakage and the number of acellular capillaries while decreasing the number of RGCs in murine retinas. In diabetic retinopathy patients, PCK1 mRNA and protein levels were up-regulated in retinal tissues. Together, PCK1 is essential for angiogenesis possibly by mediating Gα _i3 expression and Akt activation.

Cornea disease is the second cause of blindness and keratoplasty is the most commonly performed option for visual rehabilitation of patients with corneal blindness. However, the clinical treatment has been drastically limited due to a severe shortage of high-quality donor corneas. Although collagen film with outstanding biocompatibility has promising application in corneal tissue engineering, the moisturizing properties of collagen-based materials must be further improved to satisfy the requirements of clinical applications. This paper describes a novel collagen-based film with high moisture capacity reinforced by surface grafting of chondroitin sulfate. The collagen-chondroitin sulfate (abbreviated as Col-CS) film was analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy and its hydrophilic property, moisture retention, optical property, and mechanical performance had been tested. The moisture-retaining capacity is found to be improved with the introduction of chondroitin sulfate, and the Col-CS membrane performs better mechanical properties than the collagen film. Moreover, the modified film proves excellent biocompatibility for the proliferation of human corneal epithelial cells in vitro. This Col-CS film with good moisturizing properties can reduce the risk of xerophthalmia and is expected to increase the implant success rate in clinic patients with corneal defects.